The present invention relates to piston caps and, more particularly, to piston caps intended for equipping disc brakes.
Such caps are well known in the art of disc brakes and are aimed at ensuring the sealing of the cylinder of the brake motor, in order to prevent the intrusion of foreign bodies or dirt which could impede the sliding of the piston of the brake motor during a braking action. Conventionally, these caps are fastened to the sliding piston on the one hand and to the caliper of the disc brake on the other hand and are made of flexible material so as to be capable of experiencing deformation during the movement of the piston.
It can happen that, during the mounting of the disc brake and, more particularly, during the installation of the piston in its cylinder and of the cap for ensuring sealing between them, a certain quantity of air is enclosed between these two components. During braking, it is well known that there is then an emission of heat which, if communicated to the piston of the brake motor, can cause the heating of this quantity of air and therefore its expansion and an increase of pressure in the volume delimited by the piston head, the cylinder and the cap. The piston cap, because it is made of flexible material, will then be forced to expand outwards, and if there is substantial heating it can then happen that the cap comes in contact with the support of the friction material, itself brought to a high temperature. The cap will then be damaged by being burnt in the zones of contact with the friction-material support, thus making it necessary to dismantle the brake completely in order to change the cap and restore the desired sealing.